This year we published six primary studies related to DNA replication fidelity. One study showed that dNTP pool imbalances promote replication infidelity in yeast approximately equally well during leading and lagging strand DNA replication. Another study showed that the recently discovered enzyme Prim-Pol conducts translesion DNA synthesis. We showed that deposition of histone H2A.Z by the SWR-C remodeling enzyme prevents genome instability. We performed a structure-function study of DNA polymerase mu showing that it has the unique ability to conduct DNA synthesis using only the 5-prime template nucleotide in a short gap. Lastly, we conducted two studies of ribonucleotide incorporation during DNA replication in yeast. One study inferred the roles of the three major eukaryotic replicases in leading and lagging strand replication. The other study indicated that deletions of short repetitive DNA sequences result from topoisomerase 1 cleavage of the DNA backbone at ribonucleotides incorporated by DNA polymerase epsilon during leading strand replication, but not by cleavage at ribonucleotides incorporated during lagging strand replication by Pol delta or Pol alpha.